The International Patent Publication WO 01/40356A1 (filed on Sep. 18, 2000, claiming the benefit of the Chinese Patent Application No. 99125530.5 filed by the present applicants on Dec. 3, 1999) discloses a fully vulcanized powdery rubber, which means discrete, fine rubber powders having a gel content of 60 percent by weight or more and freely flowing after drying without any partitioning agents. Such powdery rubbers are obtained by irradiating a rubber latex in the absence or presence of a cross-linking agent so as to cross-link them and fix the particle size of the rubber particles, and then subjecting the irradiated latex to precipitation or spray drying. The fully vulcanized powdery rubber thus obtained has a particle size in the range of from 20 to 2000 nm and can be used as tougheners for plastics, with excellent toughening effects being achieved. However, when such a powdery rubber is used for toughening plastics, the strength, modulus and thermal properties inherent in the plastics are frequently reduced.
Since 1980s, inorganic particles have been proposed for modifying plastics. However, inorganic particles have a very high surface energy, thus if no special treatment is conducted, they are apt to agglomerate when blending with plastics, which will significantly decrease their modification effects on plastics. For example, nano-clay materials are now being used for enhancing the rigidity of polyamides, with polyamide/clay nano-composites being obtained (see, for example, “Polymers-Inorganics Nano-composites”, Series of Nano-materials and Application Technologies, the Chemical and Industrial Press, December, 2002). The clays used for preparing polyamide/clay nano-composites are conventionally sheet clays, which possess a layered structure in a nanometric scale, are natural nano-materials and are very suitable for preparing nano-composites. However, the gaps among the layers of the sheet clays are very small, thus it is impossible for organic polymers to enter said gaps to exfoliate the sheet clays in a nanometric scale. Therefore, before used for preparing such polymer/clay nano-composites, clays must be subjected to a special treatment, i.e., displacement by various organic substances, thereby obtaining nano-precursor materials containing organic functional groups, which are then compounded with polymers to form nano-composites. The process for preparing such nano-precursor materials is also called organo-modification of clays. After such an organo-modification, organic functional groups, such as organic cations and the like, are introduced to the gaps of the sheet clays, which facilitates the insertion of monomers or polymers (see, for example, “Polymer-Inorganics Nano-composites”, pp. 21-22). By intercalation-compounding, the layers of sheet clays subjected to organo-modification can be dispersed in polymer matrix in a nanometric scale, thereby obtaining polymer/clay nano-composites, which possess high strength, modulus, heat distortion temperature. The organo-modification of montmorillonite facilitates the intercalation-compounding and however, renders the preparation of composites complicated.